If you have just one heavy atom in space group P1 you can simply place it at the origin (0,0,0). Phasing with SHELXC and SHELXE should then work fine if you have SAD, MAD or SIRAS data but if you only use SIR your map will be a double image that it will not be possible to resolve. Are you sure that a heavy atom is actually present (e.g. how much anomalous signal is present)?
George Prof. George M. Sheldrick FRS Dept. Structural Chemistry, University of Goettingen, Tammannstr. 4, D37077 Goettingen, Germany Tel. +49-551-39-3021 or -3068 Fax. +49-551-39-22582 On Tue, 16 Jun 2009, 孙建 wrote: > Dear all: > I have a problem in locating heavy atom in P1 space group.My > protein is 169 residue.There are 2 molecular per asymmetry unit > according Matthews coefficient.I have soaked my protein in Hg > solution.I collected the data at 1A wavelength and the anomalous d" is > about 3 at low resolution.I loacte the heavy atom with SHELXD in SAD > method.And 1 atom with high occupancy at origin is given.Maybe just > one heavy atom is soaked in my protein .I cannot phase with the heavy > atom at origin. > I want to ask two questions: > !.Can SHELXD be used to locate just one heavy atom in P1 space group? > 2.If I find just one heavy atom in P1 space group,can I phase > it using Phenix or SHARP successfully? > Thank you! > -- > Best regard! >
